#include<stdio.h>
#include<math.h>
#include<stdlib.h>
int main(){
	int n;
	int i,temp;
	float num;
	int sum;
	while(scanf("%d",&n)!=EOF){
		sum = 0;
		num = 0;
		for(i=0;i<n;i++){
			scanf("%d",&temp);
			if(temp>0){
				num += temp*0.5;
			}else{
				num += temp;
			}
			if(num<0){
				sum+=1;
			}
		}
		printf("%d\n",sum);
	}
}